Idle Air Control (IAC)
- Before idle speed/IAC duty is checked or adjusted, ensure all wires and vacuum hoses are connected securely, accelerator cable has some play, valve clearance and timing are set to specification, and all accessories are turned off.
- Warm engine to normal operating temperature. Connect tachometer. Using a service wire, connect terminal "D" (ground) to terminal "B" (diagnostic switch). Ensure Malfunction Indicator Light (MIL) indicates a Code 12. Connect duty meter between terminal "D" (ground) and terminal "F" (duty output). If idle speed and/or IAC duty are not within specification, adjust by turning idle speed adjusting screw. See the ADJUSTMENTS
article. If idle is too high, go to next step. If idle is too low, go to step 5). If idle is unchanged (even with headlights on), go to step 7).
- If idle is too high and cannot be lowered, pinch IAC solenoid valve hose shut. If RPM does not drop, go to next step. If RPM drops, check IAC solenoid resistance. If IAC solenoid resistance is not 30-33 ohms, replace IAC solenoid. Ensure idle switch and circuit are okay. If Red/White wire from ECM (terminal A4) to IAC is not grounded, replace ECM with a known-good unit and recheck system.
- If engine speed does not reduce, ensure air intake system is free from vacuum leaks. If there are no vacuum leaks, adjust duty and idle speed by turning idle speed adjusting screw. Refer to the ADJUSTMENTS
article. If engine speed is still not adjustable, check air valve for proper operation.
- If idle is too low and cannot be increased, ensure air is being drawn into IAC hose to air cleaner case. If engine speed increases, adjust duty and idle speed. If idle remains unchanged, check IAC solenoid resistance. If IAC solenoid resistance is not 30-33 ohms, replace IAC solenoid.
- Check for clogged IAC hose, open circuit in Red/White wire or poor connection at IAC solenoid. If okay, replace ECM with a known-good unit and recheck system.
- If idle speed remains unchanged, turn ignition off. Disconnect ECM connector. If resistance between terminals A4 and A13 is 30-33 ohms, check connector terminal. If connection is okay, replace ECM with a known-good unit and recheck. If resistance reading is not 30-33 ohms, check for poor terminal connection or an open wire in harness. If ECM terminal connection and wire harnesses are okay, replace IAC solenoid.
Courtesy of SUZUKI OF AMERICA CORP.